Fire resistant resin compositions

ABSTRACT

This invention relates to flame retardants for polyester and polyamide compositions, and specifically relates to compositions containing (1) about 30 to about 70 weight percent of a polyester or a synthetic, aliphatic polyamide; (2) about 15 to about 40 weight percent of glass or mineral reinforcing agent; and (3) a flame retardant of (a) about 20 to about 30 weight percent of melamine phosphate and up to about 10 weight percent of a charring catalyst; (b) about 15 to about 30 weight percent of melamine phosphate, up to about 10 weight percent of a charring catalyst and up to about 10 weight percent of a char former; (c) about 25 to about 30 weight percent of melamine pyrophosphate; (d) about 15 to about 30 weight percent of melamine pyrophosphate and up to about 10 weight percent of a charring catalyst; or (e) about 15 to about 30 weight percent of melamine pyrophosphate, up to about 10 weight percent of a charring catalyst and up to about 10 weight percent of a char former, wherein all percents by weight are based on the total weight of (1)+(2)+(3) only.

FIELD OF THE INVENTION

This invention relates to resin compositions which have a combination of good physical properties and good fire resistance.

TECHNICAL BACKGROUND

Synthetic resins, including polyesters and aliphatic polyamides, such as nylon-6,6 and nylon-6, and copolymers thereof, are often used for molded articles and fibers. In many uses, particularly for molded articles, it is preferred if the resin has improved resistance to fire, compared to the resin alone. This is often attained by the addition of various agents which improve the basic fire resistance of the resin, but sometimes these agents degrade or diminish other physical properties of the resin. Since resins are widely used, compositions which have improved fire resistance but yet retain the desirable physical properties of the resin are constantly being sought.

German Patents 2,150,484 and 2,130,793, and A. E. Lipska, Comb. Inst. Arizona State Univ., West. State Sect. Combust, Inst. WSCI, 1973, report that certain tungsten compounds can be used in various ways to improve the fire resistance of polyamides. The combinations of agents described hereinafter are not disclosed in these references.

U.S. Pat. No. 4,298,518 discloses compositions containing polyamides and melamine cyanurate, which are said to have good fire resistance.

U.S. Pat. No. 3,458,470 discloses compositions containing polyamides and a variety of tungsten or molybdenum compounds, including silico- and phosphotungstic acids. These compositions are said to have good resistance to discoloration and be stable to light.

Melamine phosphate may be added to synthetic resins to improve the flame retardancy of the resins, but when heated to normal engineering polymer processing temperatures the melamine phosphate gives off so much water that the resultant mixture of the resin and the melamine phosphate has very poor physical properties.

What are needed, therefore, are flame retardant resin compositions which do not have the problems and deficiencies of the prior art.

SUMMARY OF THE INVENTION

This invention relates to flame retardants for polyester and polyamide compositions, and specifically relates to compositions containing (1) about 30 to about 70 weight percent of a polyester or a synthetic, aliphatic polyamide; (2) about 15 to about 40 weight percent of glass or mineral reinforcing agent; and (3) a flame retardant of (a) about 20 to about 30 weight percent of melamine phosphate and up to about 10 weight percent of a charring catalyst; (b) about 15 to about 30 weight percent of melamine phosphate, up to about 10 weight percent of a charring catalyst and up to about 10 weight percent of a char former; (c) about 25 to about 30 weight percent of melamine pyrophosphate; (d) about 15 to about 30 weight percent of melamine pyrophosphate and up to about 10 weight percent of a charring catalyst; or (e) about 15 to about 30 weight percent of melamine pyrophosphate, up to about 10 weight percent of a charring catalyst and up to about 10 weight percent of a char former, wherein all percents by weight are based on the total weight of (1)+(2)+(3) only.

These compositions exhibit good fire resistance and are useful as molding resins. These compositions may also include other additional fillers and additives as are commonly known in the art.

DETAILED DESCRIPTION

The composition described herein is a resin composition having both good physical properties and good flame retardancy. The composition has three components (1) a polyester or a synthetic, aliphatic polyamide; (2) a glass or mineral reinforcing agent; and (3) a flame retardant which includes a melamine phosphate compound and optionally a charring catalyst or a charring catalyst and a char former.

The first component is a polyester or a synthetic, aliphatic polyamide, which is present in an amount of about 30 to about 70 weight percent of the composition.

"Polyester" as used herein includes polymers having an inherent viscosity of 0.3 or greater and which are, in general, linear saturated condensation products of glycols and dicarboxylic acids, or reactive derivatives thereof. Preferably, they will comprise condensation products of aromatic dicarboxylic acids having 8 to 14 carbon atoms and at least one glycol selected from the group consisting of neopentyl glycol, cyclohexane dimethanol and aliphatic glycols of the formula HO(CH₂)_(n) OH where n is an integer of 2 to 10. Up to 50 mole percent of the aromatic dicarboxylic acids may be replaced by at least one different aromatic dicarboxylic acid having from 8 to 14 carbon atoms, and/or up to 20 mole percent may be replaced by an aliphatic dicarboxylic acid having from 2 to 12 carbon atoms.

The most common polyester compositions are based on polyethylene terephthalate homopolymers, polybutylene terephthalate homopolymers, polyethylene terephthalate/polybutylene terephthalate copolymers, polyethylene terephthalate/polybutylene terephthalate mixtures and mixtures thereof, although other polyester may be used as well, alone, in combination with each other, or in combination with those polyesters listed above.

"Synthetic polyamide", as used herein, includes a polymer which is made by man, and does not include natural fibers such as wools or silks. By an "aliphatic polyamide" is meant a polymer which has repeat units which include amide groups in the main chain, and in which at least some, preferably at least 50 mole percent, of these amide groups (through the nitrogen atoms and/or carbonyl carbon atoms of the amide groups) are connected to aliphatic carbon atoms. Preferred polyamides include nylon-6,6, nylon-6, nylon 6, 12, and copolymers of nylon-6,6 and nylon 6. Nylon-6,6 and nylon-6, and copolymers thereof, are especially preferred and nylon-6,6 is more preferred.

The second component in the invention is a reinforcing agent, such as a glass or mineral reinforcing agent, and which may include glass, carbon, mica and/or aramid fibers. The reinforcing agent, which is present in an amount of about 15 to about 40 weight percent, is important in obtaining the desired combination of both good physical properties and improved fire resistance in the inventive composition.

The third component of the invention is a flame retardant that includes a melamine phosphate compound and optionally either a charring catalyst or a charring catalyst and a char former. In one embodiment, the melamine phosphate compound is doped with a charring catalyst or with a charring catalyst and a char former.

The melamine phosphate compound may be melamine phosphate or melamine pyrophosphate or mixture of melamine phosphate and melamine pyrophosphate.

The flame retard ant component typically contains about 15 to about 30 weight percent of the melamine phosphate compound, based on the total weight of the inventive composition. When less than 15 weight percent of the melamine phosphate compound is present, the composition is not effective as a flame retardant. While it may be possible to use greater that 30 weight percent of a melamine phosphate compound, such amounts are not deemed to be practical because of the high costs of using such an amount of the melamine phosphate compound.

Another ingredient of the inventive composition that is part of the flame retardant is a charring catalyst. When melamine pyrophosphate is used as the melamine compound, the presence of the charring catalyst is not essential to the invention, but its use in conjunction with melamine pyrophosphate greatly reduces the amount of melamine pyrophosphate needed, as discussed below.

As used herein, the term "charring catalyst" includes metal salt of a tungstic acid or a complex oxide acid of tungsten and a metalloid, a tin oxide salt such as sodium tin oxide, and/or ammonium sulfamate. Preferred metal salts include alkali metal salts of a tungstic acid, with sodium tungstate being especially preferred. By a complex oxide acid of tungsten and a metalloid is meant a complex oxide acid formed by a metalloid such as phosphorous or silicon and tungsten. Preferred complex oxide acids include silicotungstic acid and phosphotungstic acid, with silicotungstic acid being especially preferred. If the charring catalyst is present as part of the flame retardant component of the inventive composition it is present in an amount up to about 10 weight percent based on the total weight of the inventive composition. A preferred range is from about 0.1 to about 10 weight percent, with a more preferred range being from about 0.1 to about 2 weight percent.

Another ingredient of the inventive composition that is part of the flame retardant is a char former such as a polyhydric alcohol. Other examples include novolac, vinyl alcohols and starches. In the present invention, it is preferred that the polyhydric alcohol be penterythritol or dipenterythritol. If it is present in the composition, the char former is present in amounts of up to 10 weight percent based on the total weight of the inventive composition. A preferred range is from about 0.1 to about 10 weight percent, with a more preferred range being from about 0.1 to about 2 weight percent.

The flame retardant component of the present invention includes the following combinations of a melamine phosphate compound with either a charring catalyst or a charring catalyst and a char former: (a) about 20 to about 30 weight percent of melamine phosphate and up to about 10 weight percent of a charring catalyst; (b) about 15 to about 30 weight percent of melamine phosphate, up to about 10 weight percent of a charring catalyst and up to about 10 weight percent of a char former; (c) about 25 to about 30 weight percent of melamine pyrophosphate; (d) about 15 to about 30 weight percent of melamine pyrophosphate and up to about 10 weight percent of a charring catalyst; and (e) about 15 to about 30 weight percent of melamine pyrophosphate, up to about 10 weight percent of a charring catalyst and up to about 10 weight percent of a char former.

By "melamine compound doped with a charring catalyst" is meant a melamine phosphate compound such as melamine pyrophospate that is made such that the charring catalyst is bound to the melamine pyrophosphate. The melamine compound doped with a charring catalyst may be made by preparing an aqueous solution of melamine, preparing an aqueous solution of silicotungstic acid or phosphotungstic acid, and preparing an aqueous solution of a phosphorous compound, such as H₃ PO₄ (85% acid). The tungstic acid solution is added to the phosphorous solution, and then that mixture is added to the melamine solution, wherein melamine phosphate is converted to melamine pyrophosphate through the loss of a water molecule. The resulting solution is vacuum dried to produce the doped melamine phosphate compound. The mole ratio of the melamine to phosphorous in the solution should be from 2:1 to 1:2. The number of moles of the charring catalyst should be from 0.01 to 0.5 moles per mole of melamine phosphate compound, and preferably 0.1 moles per mole of melamine compound. There may not be a 100% conversion of melamine phosphate to melamine pyrophosphate when the doped melamine compound is made, so that while the doped melamine compound is is primarily melamine pyrophosphate, it may also include unconverted melamine phosphate.

The melamine compound that is doped with a charring catalyst may also be made by contacting, in an aqueous medium, melamine and silicotungstic acid or phosphotungstic acid in a molar ratio of from about 1 to about 24 moles of melamine per mole of the tungsten compound to prepare "melamine salts" of the tungstic acids. It is preferred that the contacting be carried out at about 50° C. to about 100° C. It is believed that the melamine not only forms salts with the tungsten compound used, but also solvates the resulting salt much like water forms hydrates. Cyanuric acid may also be present so that the melamine forms a "mixed salt" with cyanuric acid and the silico- or phosphotungstic acid.

It has also been discovered that for compositions that include a synthetic, aliphatic polyamide and a glass or mineral reinforcing agent, melamine pyrophosphate alone is effective as a flame retardant if used in a proportion of about 25 to about 30 weight percent. If used alone as a flame retardant, it is preferred that the melamine pyrophosphate be preheated before it is added to the polyamide and reinforcing agent. The heating conditions are not critical, and are typically in a temperature range of about 270 C. for about 15 minutes.

The compositions described herein have improved fire resistance compared to the resin alone, and are particularly useful as molding resins for making parts such as electrical and electronic parts such as bobbins, coil forms, connectors, fasteners, and for parts in equipment such as circuit breakers. These compositions also retain the good physical properties of the resins, that is desirable mechanical properties particularly toughness. Toughness may be roughly estimated as being proportional to the product of the tensile strength and elongation, so the higher either or both of these are, the tougher the polymer. It is preferred that the composition be fire resistant enough so that it has a rating of V0 in the Underwriters Laboratory test UL-94, at a thickness of 0.16 cm ( 1/16 inch).

It is also preferred that the melmine phosphate compound, reinforcing agent and charring catalyst be relatively well dispersed in the resin. A preferred degree of dispersion can be attained by producing the composition in any of a number of different types of equipment which are commonly used to disperse materials in polymers. For instance, a twin screw extruder with appropriate mixing screw sections can be used to satisfactorily melt mix the ingredients. It is also believed that the dispersion of the charring catalyst in the polymer is aided by starting with tungsten compound having relatively small particle sizes.

EXAMPLES

The following abbreviations are used in the Examples and the Tables set out below:

RM--reinforcing material

MC--melamine phosphate compound

CC--charring catalyst

CF--char former

MP--melamine phosphate

MPP--melamine pyrophosphate

PTA--phosphotungstic acid

STA--silicotungstic acid

NYADG--mica filler

NATO--sodium tin oxide

Unless otherwise indicated, the following procedure was used in the examples. The resin used in the Example was ground, and then the resin, a reinforcing material, a melamine phosphate compound, a charring catalyst or a charring catalyst and a char former were thoroughly mixed, which usually took about 30 minutes. In the examples where a doped melamine compound was used, the doped melamine compound was prepared as set forth in the Example, and then was thoroghly mixed with the resin and reinforcing material.

The resin mixture was then dried under standard conditions, and then extruded on either a 28 mm or a 30 mm Werner & Pfleiderer twin screw extruder, using a screw design having a mid range screw severity, at a melt temperature of 270°-300° C., and at rates of 11.3-15.9 kg per hour. Bars of 1/16" were molded on a 0.043 kg (1.5 oz) molding machine. Standard molding conditions for the resin mixtures were used.

These resin mixtures were then molded into bars using typical injection molding machines, ranging from laboratory sized machines to commercial sized machines. Melt temperatures were typically about 280°-300° C., and mold temperatures were typically 45°-100° C. The molded bars were then tested for a flammability rating in the UL-94 test at 0.16 cm thickness.

EXAMPLES--NYLON 6,6 RESIN

In the following Examples, Zytel® 101 nylon 6,6 resin sold by DuPont was used. The data from these Examples are summarized in Tables 1 and 2.

EXAMPLES 1-3

In these Examples, molded bars were made using glass as the reinforcing material, melamine phosphate sold by Chemie Linz of Linz, Austria, under the trade name MELAPUR-MPH as the melamine phosphate compound, and phosphotungstic acid as the charring catalyst. The molded bars in these Examples were all V0 under UL94.

EXAMPLE 4

A molded bar was made as in Examples 1-3, except that silicotungstic acid was used as the charring catalyst. The molded bar passed UL94 with a V0 rating.

EXAMPLE 5 AND COMPARATIVE EXAMPLE 6

Molded bars were made as in Example 4, except that 30.0 wt. % mica filler was used as the reinforcing agent. Example 5 had 25.0 wt % melamine phosphate and 1 wt % silicotungstic acid and passed UL94 with a V0, but Example 6 had only 15.0 wt % melamine phosphate and 1 wt % silicotungstic acid and did not pass UL94.

EXAMPLES 7-10

In these Examples, molded bars were made using melamine pyrophosphate as the melamine phosphate compound, and no charring catalyst was used. The melamine pyrophosphate is available from Cytek of West Patterson, N.J., and is sold under the tradename AEROGUARD MPP. The Examples show that at a melamine phosphate compound loading of 25 to 30 wt % the molded bars are all V0. Examples 7 and 8 produced some foam on extrusion. In Examples 9 and 10 the melamine pyrophosphate was heated at 270 C. for 15 minutes before it was added to the resin and glass, which resulted in a significant improvement it the flame retardancy of the melamine pyrophosphate.

EXAMPLE 11

In this Example, molded bars were made as in Example 7 except that a charring catalyst was added to the composition. There was greatly reduced foaming in this Example compared to Examples 7 and 8, and the bar produced was V0.

EXAMPLE 12

A molded bar was made with glass and a melamine phosphate compound doped with a charring catalyst made by making a solution of 98 g. of melamine in 700 g water and a solution of 12 g of silicotungstic acid in 12 g. water which was added into 84 g. H₃ PO₄ (85% acid) in 300 g water. The two solutions were mixed together and then vacuum dried at 90 C. The molded bar was V0.

EXAMPLE 13

A molded bar was made as in Example 1, except that the melamine phosphate compound was doped with the charring catalyst by making a solution of 98 g. of melamine in 700 g water and a solution of 2 g of silicotungstic acid in 12 g. water which was added into 84 g. H₃ PO₄ (85% acid) in 300g water. The two solutions were mixed together and then vacuum dried at 90 C. The molded bar was V0.

EXAMPLE 14

A molded bar was made as in Example 13, except that the melamine phosphate compound was doped with the charring catalyst by making a solution of 98 g. of melamine in 700 g water and a solution of 12 g of silicotungstic acid in 12 g. water which was added into 84 g. H₃ PO₄ (85% acid) in 300 g water. The two solutions were mixed together and then vacuum dried at 90 C. The molded bar was V0.

EXAMPLE 15

A molded bar was made as in Example 13, except that the melamine phosphate compound was doped with the charring catalyst by making a solution of 98 g. of melamine in 700 g water and 5 g Na₂ SnO₃ in 300 g water and a solution of 84 g. H₃ PO₄ (85% acid) in 300 g water. The two solutions were mixed together and then vacuum dried at 90 C. The molded bar was V0.

EXAMPLES 16-17

Molded bars were made as in Example 13, except that the melamine phosphate compound was doped with the charring catalyst by making a solution of 98 g. of melamine in 700 g water and a solution of 16 g of phosphotungstic acid in 20 g. water which was added into 84 g. H₃ PO₄ (85% acid) in 300 g water. The two solutions were mixed together and then vacuum dried at 90 C. The molded bars were V0.

EXAMPLE 18

A molded bar was made as in Example 14, except that the bar was made to a thickness of 1/32 inch. This bar was V0.

EXAMPLES 19-20

Molded bars were made as in the previous Example, except that the melamine phosphate compound was doped with the charring catalyst by making a solution of 98 g. of melamine phosphate in 700 g water and a solution of 1 g of silicotungstic acid in 20 g. water. The two solutions were mixed together and then vacuum dried at 90 C. The molded bars were V0.

EXAMPLES--POLYESTER RESIN

Molded bars were made as in the previous Examples, except that Rynite® 3934 polyester sold by DuPont of Wilmington, Del. or Crystar® 3935 polyester sold by Shell of Houston, Tex., was used as the resin. These results are summarized in Tables 3 and 4.

COMPARATIVE EXAMPLE 21

A molded bar was made using Rynite® 3934 polyester resin and melamine phosphate but no charring catalyst. The molded bar failed UL94.

EXAMPLES 22, 24 AND 26-27 AND COMPARATIVE EXAMPLES 23 AND 25

In these Examples, molded bars were made as in Example 21 except that silicotungstic acid was used as a charring catalyst. Examples 22 and 24 were V0. Example 23 was almost V0, but was a V2 because of the low amount of melamine phosphate relative to the charring catalyst. Example 25 failed because of a low amount of melamine phosphate relative to the charring catalyst. Examples 26 and 27 were V0.

EXAMPLES 28-29 and COMPARATIVE EXAMPLE 30

Molded bars were made as in Example 21, except that silicotungstic acid and a char former of dipentaerythritol were compounded with the resin. The molded bars for Examples 28 and 29 were V0. Comparative Example 30 failed because of the insufficient amount of melamine phosphate present.

EXAMPLES 31-32

Molded bars were made as in Example 21, except that the melamine phosphate compound was melamine pyrophosphate. The molded bars were V0.

EXAMPLE 33

Molded bars were made as in Example 31, except that a charring catalyst was added to the composition. The molded bar was V0.

EXAMPLE 34

A molded bar was made as in Example 21, except that the melamine phosphate compound was doped with the charring catalyst by making a solution of 98 g. of melamine in 700 g water and a solution of 16 g of silicotungstic acid in 20 g. water which was added into 84 g. H₃ PO₄ (85% acid) in 300 g water. The two solutions were mixed together and then vacuum dried at 90 C. The molded bar was V0.

EXAMPLE 35

A molded bar was made as in Example 21, except that the melamine phosphate compound was doped with the charring catalyst by making a solution of 98 g. of melamine in 700 g water and a solution of 16 g of phosphotungstic acid in 20 g. water which was added into 84 g. H₃ PO₄ (85% acid) in 300 g water. The two solutions were mixed together and then vacuum dried at 90 C. The molded bar was V0.

EXAMPLES 36-37

Molded bars were made as in Example 21, except that Crystar® 3935 polyester resin was used and the melamine phosphate compound was doped with the charring catalyst as made in Example 16. The molded bars were V0.

EXAMPLES 38-39

Molded bars were made as in Example 36 except that the melamine phosphate compound was doped with the charring catalyst as made in Example 19. The molded bars were V0.

EXAMPLES 40-41 AND COMPARATIVE EXAMPLE 42

Molded bars were made as in the previous Example, except that Rynite® 3934 polyester resin was used. The molded bars were V0. Example 42 included 15 wt % of the doped melamine phosphate compound, and failed the UL test.

EXAMPLES--NYLON 6 RESIN

Molded bars were made as in the previous Examples, except that Ultramid B3 nylon 6 sold by BASF of Ludwigshafen, Germany was used as the resin. These results are summarized in Table 5.

EXAMPLE 43

A molded bar made from Ultramid nylon 6 resin, glass reinforcing material, and a melamine phosphate compound doped with the charring catalyst made by making a solution of 98 g. of melamine in 700 g water and a solution of 16 g of silicotungstic acid in 30 g. water which was added into 84 g. H₃ PO₄ (85% acid) in 300 g water. The two solutions were mixed together and then vacuum dried at 90 C. The molded bar was V0.

EXAMPLES 44-45

Molded bars were made as in the previous Example, except that the melamine phosphate compound was doped with the charring catalyst as made in Example 16. The molded bar from Example 44 was V0, but the bar from Example 45 V0 failed UL94.

EXAMPLES 46-47

Molded bars were made as in Example 43, except that the melamine phosphate compound was doped with the charring catalyst as made in Example 19. The molded bar from Example 46 was V0, but the bar from Example 47 V0 failed UL94.

                                      TABLE 1                                      __________________________________________________________________________     EXAMPLES WITH NYLON 6,6 RESINS                                                 Ex. No.                                                                             wt %. resin                                                                          RM   wt % RM                                                                              MC wt % MC                                                                              CC   wt % CC                                                                             UL94                                  __________________________________________________________________________     1    50.3  glass                                                                               24.4  MP 24.4  PTA  1.1  V0                                    2    49.7  glass                                                                               24.3  MP 24.3  PTA  1.7  V0                                    3    49.4  glass                                                                               24.2  MP 24.2  PTA  2.2  V0                                    4    50.2  glass                                                                               25.0  MP 23.1  STA  1.7  V0                                    5    44.0  NYADG                                                                               30.0  MP 25.0  STA  1.0  V0                                    C6*  54.0  NYADG                                                                               30.0  MP 15.0  STA  1.0  V2                                    7    50.0  glass                                                                               25.0  MPP                                                                               25.0            V0                                    8    45.0  glass                                                                               25.0  MPP                                                                               30.0            V0                                    9    50.0  glass                                                                               25.0  MPP                                                                               25.0            V0                                    10   45.0  glass                                                                               25.0  MPP                                                                               30.0            V0                                    11   50.0  glass                                                                               25.0  MPP                                                                               24.0  STA  1.0  V0                                    __________________________________________________________________________      *"C" INDICATES A COMPARATIVE EXAMPLE                                     

                  TABLE 2                                                          ______________________________________                                         EXAMPLES WITH NYLON 6,6 RESINS AND DOPED                                       MELAMINE COMPOUND                                                              Ex.  wt %.                   DOPED                                             No.  resin   RM      wt % RM MC wt % CC    UL94                                ______________________________________                                         12   50.0    glass   25.0    25.0    STA   V0                                  13   50.0    glass   25.0    25.0    STA   V0                                  14   50.0    glass   25.0    25.0    STA   V0                                  15   50.0    Glass   25.0    25.0    NATO  V0                                  16   50.0    glass   25.0    25.0    PTA   V0                                  17   55.0    glass   25.0    20.0    PTA   V0                                  18   50.0    glass   25.0    25.0    STA   V0                                  19   50.0    glass   25.0    20.0    STA   V0                                  20   55.0    glass   25.0    20.0    STA   V0                                  ______________________________________                                    

                                      TABLE 3                                      __________________________________________________________________________     EXAMPLES WITH POLYESTER RESINS                                                 Ex. No.                                                                             wt %. resin                                                                          RM wt % RM                                                                              MC wt % MC                                                                              CC wt % CC                                                                             CF   wt % CF                                                                             UL94                            __________________________________________________________________________     C21  50.0  glass                                                                             25.0  MP 25.0                    fail                            22   49.5  glass                                                                              24.75                                                                               MP  24.75                                                                               STA                                                                               1.0            V0                              C23  53.7  glass                                                                             25.2  MP 20.1  STA                                                                               1.0            V2                              24   44.0  glass                                                                             25.0  MP 30.0  STA                                                                               1.0            V0                              C25  58.4  glass                                                                             24.8  MP 14.8  STA                                                                               2.0            fail                            26   53.4  glass                                                                             24.7  MP 19.9  STA                                                                               2.0            V0                              27   48.0  glass                                                                             30.0  MP 20.0  STA                                                                               2.0            V0                              28   52.0  glass                                                                             30.0  MP 15.0  STA                                                                               1.0  DIPEN                                                                               2.0  V0                              29   48.0  glass                                                                             30.0  MP 20.0  STA                                                                               1.0  DIPIN                                                                               1.0  V0                              C30  54.5  glass                                                                             30.0  MP 12.5  STA                                                                               1.0  DIPEN                                                                               2.0  fail                            31   50.0  glass                                                                             25.0  MPP                                                                               25.0                    V0                              32   45.0  glass                                                                             25.0  MPP                                                                               30.0                    V0                              33   50.0  glass                                                                             25.0  MPP                                                                               24.0  STA                                                                               1.0            V0                              __________________________________________________________________________

                  TABLE 4                                                          ______________________________________                                         EXAMPLES WITH POLYESTER RESINS AND DOPED                                       MELAMINE COMPOUND                                                              Ex.  wt %.                   DOPED                                             No.  resin   RM      wt % RM MC wt % CC    UL94                                ______________________________________                                         34   50.0    glass   25.0    25.0    STA   V0                                  35   50.0    glass   25.0    25.0    PTA   V0                                  36   50.0    glass   25.0    25.0    PTA   V0                                  37   55.0    glass   25.0    20.0    STA   V0                                  38   50.0    glass   25.0    25.0    STA   V0                                  39   55.0    glass   25.0    20.0    STA   V0                                  40   50.0    glass   25.0    25.0    STA   V0                                  41   55.0    glass   25.0    20.0    STA   V0                                  C42  60.0    glass   25.0    15.0    STA   fail                                ______________________________________                                    

                  TABLE 5                                                          ______________________________________                                         EXAMPLES WITH NYLON 6 RESINS AND DOPED                                         MELAMINE COMPOUND                                                              Ex.  wt %.                   DOPED                                             No.  resin   RM      wt % RM MC wt % CC    UL94                                ______________________________________                                         43   50.0    glass   25.0    25.0    STA   V0                                  44   50.0    glass   25.0    25.0    PTA   V0                                  C45  55.0    glass   25.0    20.0    PTA   fail                                46   50.0    glass   25.0    25.0    STA   V0                                  C47  55.0    glass   25.0    20.0    STA   fail                                ______________________________________                                    

Although particular embodiments of the present invention have been described in the foregoing description, it will be understood by those skilled in the art that the invention is capable of numerous modifications, substitutions and rearrangements without departing from the spirit or essential attributes of the invention. Reference should be made to the appended claims, rather than to the foregoing specification, as indicating the scope of the invention.

In addition to the components discussed above, the compositions of this invention may contain additives commonly employed with synthetic resins, such as colorants, mold release agents, antioxidants, tougheners, nucleating agents, ultraviolet light and heat stabilizers and the like. An example of a common filler is magnesium hydroxide. 

What is claimed is:
 1. A composition comprising:(1) about 30 to about 70 weight percent of a polyester or a synthetic, aliphatic polyamide; (2) about 15 to about 40 weight percent of a reinforcing agent; and (3) a flame retardant selected from the group consisting of(a) about 20 to about 30 weight percent of melamine phosphate and up to about 10 weight percent of a charring catalyst; (b) about 15 to about 30 weight percent of melamine phosphate, up to about 10 weight percent of a charring catalyst and up to about 10 weight percent of a char former; (c) about 25 to about 30 weight percent of melamine pyrophosphate; (d) about 15 to about 30 weight percent of melamine pyrophosphate and up to about 10 weight percent of a charting catalyst; and (e) about 15 to about 30 weight percent of melamine pyrophosphate, up to about 10 weight percent of a charring catalyst and up to about 10 weight percent of a char former, wherein all percents by weight are based on the total weight of (1)+(2)+(3) only.
 2. The composition of claim 1 wherein the charring catalyst is phosphotungstic acid or silicotungstic acid.
 3. The composition of claim 1 wherein the charring catalyst is an alkali metal salt of tungstic acid.
 4. The composition of claim 1 wherein the amount of the charring catalyst is about 0.1 to about 10 weight percent.
 5. The composition of claim 1 wherein the amount of the charring catalyst is about 0.1 to about 2 weight percent.
 6. The composition of claim 1 wherein the char former is a polyhydric alcohol.
 7. The composition of claim 6 wherein the polyhydric alcohol is pentaerythritol.
 8. The composition of claim 1 wherein the amount of the char former is about 0.1 to about 10 weight percent.
 9. The composition of claim 1 wherein the amount of the char former is about 0.1 to about 2 weight percent.
 10. The composition of claim 1 wherein said polyamide is selected from the group consisting of nylon-6,6, nylon-6 and copolymers thereof.
 11. The composition of claim 1 wherein said reinforcing agent is glass, carbon, mica, aramid fibers or mixtures thereof. 